Method of treating diabetes mellitus

ABSTRACT

The present invention relates to the use of a compound of the formula   &lt;CHEM&gt; wherein R1, R2, R3 and R4 are each independently a C1-C6 alkyl group, for the preparation of a pharmaceutical composition for lowering blood glucose and treating diabetes mellitus.

Diabetes mellitus is a disorder of carbohydrate metabolism characterized by hyperglycemia. In general, the hyperglycemia associated with diabetes mellitus is caused by absolute or relative insulin deficiency, or insulin resistance, or both.

Insulin is a hormone secreted by the β-cells of the islets of Langerhans in the pancreas. Insulin regulates glucose metabolism and promotes the transport of glucose from the blood to the skeletal muscle, adipose tissue, and other tissues so that it can be utilized as an energy source or stored as glycogen. Glucagon is a hormone secreted by the α-cells of the islets of Langerhans in the pancreas and generally has effects which counteract the effects of insulin.

Physiologic states in which there is an absolute or relative insulin deficiency, or insulin resistance, or both, result in disease states such as diabetes mellitus. An absolute insulin deficiency occurs when the pancreatic β-islet cells no longer secrete significant amounts of insulin. A relative insulin deficiency occurs where the ratio of glucagon to insulin secreted by the pancreas is consistently higher than that found in normal subjects. Insulin resistance can occur where there is impaired insulin action due to anti-insulin receptor antibodies, reduced insulin receptors or other receptor or post-receptor defects.

Diabetes mellitus can be classified as follows:

1. Insulin-dependent diabetes mellitus (also called type I diabetes);

2. Non-insulin-dependent diabetes mellitus (also called type II diabetes).

Patients with insulin-dependent diabetes mellitus (IDDM) have little or no endogenous insulin secretory capacity. These patients develop extreme hyperglycemia and are susceptible to developing ketosis and ketoacidosis. Patients with non-insulin-dependent diabetes mellitus (NIDDM) retain the ability to secrete insulin. However, this insulin secretion is at reduced levels or is overbalanced by excessive secretion of counteracting hormones such as glucagon. In either case there is a relative insulin deficiency. Patients with NIDDM also develop hyperglycemia but are not as susceptible to ketosis or ketoacidosis as those patients with IDDM.

In general, diabetes mellitus develops in response to damage to the insulin-secreting β-islet cells of the pancreas. This damage can result from primary diabetes mellitus, in which the β-islet cells are destroyed by the autoimmune system, or as a secondary diabetic response to other primary diseases, such as pancreatic disease, excesses of counterinsulin hormones, drug-induced conditions or genetic abnormalities other than that associated with primary diabetes. In either case, the β-islet cells cannot produce sufficient insulin to adequately transport the blood glucose from the blood to the insulin sensitive tissues.

Disease states such as diabetes mellitus therefore result in hyperglycemia (abnormally high levels of blood glucose), glycosuria (excessive excretion of glucose in the urine) and decreased glycogen levels in the liver, as well as other metabolic consequences. In addition to the metabolic consequences of the disease, there are also a number of degenerative complications of the disease which result from these metabolic consequences. For example, diabetic retinopathy, diabetic neuropathy, nephropathy, atherosclerosis, cardiomyopathy, dermopathy, diabetic foot syndrome and peripheral vascular disease are all complications associated with and resulting from diabetes mellitus. It is generally believed that these degenerative complications are caused by the metabolic consequences of the disease. It is also generally believed by those skilled in the art that reduction of the hyperglycemia associated with diabetes mellitus in particular will delay or prevent these degenerative complications in patients afflicted with diabetes mellitus [see Brownlee and Cerami, Annu. Rev. Biochem. 50, 385 (1981)]. Furthermore, in severe hyperglycemia, the blood glucose levels can become so high that hyperosmolar non-ketotic coma can result. Reduction of blood glucose levels in diabetic patients can thus prevent hyperosmolar non-ketotic coma resulting from hyperglycemia.

Some pharmacologically active agents, such as alloxan, can produce a drug-induced diabetic condition in animals. Alloxan, or mesoxalylurea, selectively destroys the capacity of the β-islet cells of the pancreas to produce insulin. Alloxan-treated animals retain very little or no endogenous insulin secretory capacity and develop hyperglycemia in a manner similar to that in IDDM. As such, alloxan-treated animals provide a standard experimental model for diabetes mellitus in man which is well known and appreciated by those skilled in the art [see R. H. Bell and R. J. Hye, J. Surg. Res. 35: 433-60 (1983)]. The effect of experimental agents on the hyperglycemia of the alloxan-treated animals can thus be studied to determine whether these agents reduce the hyperglycemia associated with the experimental diabetes. Positive results in this experimental model are well known and appreciated to be reasonably predictive of results in humans with diabetes mellitus.

The present invention provides a method of lowering blood glucose in a patient afflicted with diabetes mellitus comprising administering to said patient an effective blood glucose lowering amount of a compound of formula (1) ##STR2## wherein R₁, R₂, R₃ and R₄ are each independently a C₁ -C₆ alkyl group. The present invention further provides a method of treating a patient afflicted with diabetes mellitus comprising administering to said patient an effective blood glucose lowering amount of a compound of formula (1). The present invention thus provides a means for lowering blood glucose and thereby delaying or preventing the diabetic complications resulting from hyperglycemia associated with diabetes mellitus.

As used herein, the term "C₁ -C₆ alkyl group" means and includes saturated alkyl groups of straight, cyclic or branched-chain configuration made up of from one to six carbon atoms. Included within the scope of this term are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tertiarybutyl and the like. The compound of formula (1) wherein R₁, R₂, R₃ and R₄ are each tertiarybutyl, or bis(3,5-di-tertiary-butyl-4-hydroxyphenylthio) methane, is preferred in the method of use according to the present invention.

As used herein, the term "patient" refers to warm-blooded animals or mammals, including humans, who are afflicted with diabetes mellitus, IDDM or NIDDM, as either a primary or as a secondary disease state. Treatment of a patient afflicted with diabetes mellitus refers to the reduction of the patient's blood glucose levels.

Diagnosis of patients afflicted with diabetes mellitus is well within the ability and knowledge of one skilled in the art. For example, individuals who have symptoms of polydipsia, polyuria, polyphagia and weight loss coupled with an elevation of plasma glucose over normal levels are generally considered within the diagnosis of diabetes mellitus. A clinician skilled in the art can readily identify, by the use of clinical tests, physical examination and medical/family history, those patients who are afflicted with diabetes mellitus.

An effective blood glucose lowering amount of a compound of formula (1) is that amount, either in single or in multiple doses, which is effective in significantly reducing plasma glucose levels in a patient afflicted with diabetes mellitus. An effective dose can be readily determined by the use of conventional techniques and by observing results obtained under analogous circumstances. In determining the effective dose, a number of factors are considered including, but not limited to: the patient's size, age, and general health; the degree of or involvement or the severity of the disease; the response of the individual patient; the particular compound administered; the mode of administration; the bioavailability characteristics of the preparation administered; the dose regimen selected; and the use of concomitant medication.

An effective blood glucose lowering amount of a compound of formula (1) will generally vary from about 1 milligram per kilogram of body weight per day (mg/kg/day) to about 5 grams per kilogram of body weight per day (gm/kg/day). A daily dose of from about 1 mg/kg to about 500 mg/kg is preferred.

In effecting treatment of a patient, a compound of formula (1) can be administered in any form or mode which makes the compound bioavailable in effective amounts, including oral and parenteral routes. For example, the compound can be administered orally, subcutaneously, intramuscularly, intravenously, transdermally, intranasally, rectally, and the like. Oral administration is generally preferred. One skilled in the art of preparing formulations can readily select the proper form and mode of administration depending upon the severity of the disease and other relevant circumstances.

Compounds of the present invention can be administered in the form of pharmaceutical compositions or medicaments which are made by combining compounds of formula (1) with pharmaceutically acceptable carriers or excipients, the proportion and nature of which are determined by the chosen route of administration, and standard pharmaceutical practice.

The pharmaceutical compositions or medicaments are prepared in a manner well known in the pharmaceutical art. The carrier or excipient may be a solid, semi-solid, or liquid material which can serve as a vehicle or medium for the active ingredient. Suitable carriers or excipients are well known in the art. The pharmaceutical composition may be adapted for oral or parenteral use and may be administered to the patient in the form of tablets, capsules, suppositories, solution, suspensions, or the like.

The pharmaceutical compositions may be administered orally, for example, with an inert diluent or with an edible carrier. They may be enclosed in gelatin capsules or compressed into tablets. For the purpose of oral therapeutic administration, compounds of the present invention may be incorporated with excipients and used in the form of tablets, troches, capsules, elixirs, suspensions, syrups, wafers, chewing gums and the like. These preparations should contain at least 4% of the active ingredient, but may be varied depending upon the particular form and may conveniently be between 4% to about 70% of the weight of the unit. The amount of the active ingredient present in compositions is such that a unit dosage form suitable for administration will be obtained.

The tablets, pills, capsules, troches and the like may also contain one or more of the following adjuvants: binders, such as microcrystalline cellulose, gum tragacanth or gelatin; excipients, such as starch or lactose, disintegrating agents such as alginic acid, Primogel, corn starch and the like; lubricants, such as magnesium stearate or Sterotex; glidants, such as colloidal silicon dioxide; and sweetening agents, such as sucrose or saccharin may be added or flavoring agents, such as peppermint, methyl salicylate or orange flavoring. When the dosage unit form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier such as polyethylene glycol or a fatty oil. Other dosage unit forms may contain other various materials which modify the physical form of the dosage unit, for example, as coatings. Thus, tablets or pills may be coated with sugar, shellac, or other enteric coating agents. A syrup may contain, in addition to the active ingredient, sucrose as a sweetening agent and certain preservatives, dyes and colorings and flavors. Materials used in preparing these various compositions should be pharmaceutically pure and non-toxic in the amounts used.

For the purpose of parenteral administration, the compounds of the present invention may be incorporated into a solution or suspension. These preparations should contain at least 0.1% of a compound of the invention, but may be varied to be between 0.1 and about 50% of the weight thereof. The amount of the active ingredient present in such compositions is such that a suitable dosage will be obtained.

The solutions or suspensions may also include one or more of the following adjuvants: sterile diluents such as water for injection, saline solution, fixed oils, polyethylene glycols, glycerine, propylene glycol or other synthetic solvents; antibacterial agents such as benzyl alcohol or methyl paraben; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylene diaminetetraacetic acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of toxicity such as sodium chloride or dextrose. The parenteral preparation can be enclosed in ampules, disposable syringes or multiple dose vials made of glass or plastic.

In the end use application provided by the present invention, the preferred compound of formula (1) is bis(3,5-di-tertiary-butyl-4-hydroxyphenylthio)methane. This preferred compound can be prepared by methods well known and appreciated by those of ordinary skill in the art. For example, the compound can be prepared by treating 2,6-di-tertiary-butyl-4-mercaptophenol with 1,3,5-trioxane in the presence of acetonitrile and DOWEX 50 resin under reflux conditions. 2,6-Di-tertiary-butyl-4-mercaptophenol can be prepared as described, for example, by Krauss in U.S. Pat. No. 4,734,527.

The following examples illustrate the preparation and use of bis(3,5-di-tertiary-butyl-4-hydroxyphenylthio) methane. These examples are illustrative only and are not intended to limit the scope of the invention in any way.

EXAMPLE 1 Preparation of Bis(3,5-di-tertiary-butyl-4-hydroxyphenylthio)methane

Combine acetonitrile [1800 milliliters (ml)], 1,3,5-trioxane [71.0 grams (gm), 0.79 moles (mol)], 2,6-di-tertiary-butyl-4-mercaptophenol [678.4 gm, 2.85 mol]and 2.5 gm DOWEX 50 resin in a three-necked flask with a thermowell. Bring the mixture to reflux under a nitrogen atmosphere and maintain for 36-48 hours to provide the title compound.

Filter the mixture to remove the DOWEX 50 resin and concentrate the filtrate in vacuo to give an amber oil. Dissolve the oil in 1 liter of ethanol at 70 degrees Celsius (° C.) and add 125 ml of water. Allow the mixture to cool to ambient temperature overnight while stirring. Collect the resulting crystalline product by filtration and wash the filter cake with 75 ml of cold ethanol/water (90/10). Recrystallize the product from ethanol/water and collect by filtration. Wash the filter cake with 50 ml of cold ethanol and dry the product in a vacuum oven at 50° C. and 15 mm Hg overnight to yield 406.9 gm of the purified title compound as a white solid. Melting point 94-95° C. Elemental analysis:

Calculated--C=71.3%, H=9.07%;

Found--C=71.3%, H=9.09%.

EXAMPLE 2 Hypoglycemic Effect of Bis(3,5-di-tertiary-butyl-4-hydroxyphenylthio)methane in Alloxan-Treated Rats

Normal male, Sprague-Dawley, rats of comparable weight and age are assigned to one of three groups and are treated as follows:

1. Non diabetic control-10 animals receive rat chow for two weeks;

2. Diabetic control-25-30 animals receive rat chow for two weeks;

3. Compound A-25-30 animals receive rat chow containing bis(3,5-di-tertiary-butyl-4-hydroxyphenyl-thio)methane, 1% (w/w), for two weeks.

At the end of the 2 week treatment, animals in groups 2 and 3 receive a single dose of alloxan (40 milligrams/kilogram of body weight) by intravenous administration and animals in group 1 receive a comparable dose of saline. Animals continue to receive the diet indicated for their group for an additional 5 days. On the fifth day after alloxan or saline treatment, urine is collected for 4 hours and analyzed for glucose. Animals are then fasted overnight and are sacrificed by exsanguination under metophane anesthesia. Blood plasma samples are analyzed for glucose, triglycerides and insulin. Pancreases are collected for histological examination.

The results of this study, presented in Table 1, clearly show that treatment with bis(3,5-di-tertiary-butyl-4-hydroxyphenyl-thio)methane significantly reduces blood glucose in rats with alloxan-induced diabetes compared to the alloxan-diabetic controls

                  TABLE 1                                                          ______________________________________                                         Effect of Bis(3,5-di-tertiary-butyl-4-                                         hydroxyphenylthio)methane in Alloxan-Treated Rats                                       Urine     Plasma    Tri-                                              Treatment                                                                               Glucose   Glucose   glycerides                                                                             Insulin                                   group    (mg/4 hr) (mg/dl)   (mg/dl) (μU/ml)                                ______________________________________                                         Nondiabetic                                                                             None      128 ± 12.sup.a*                                                                       15 ± 3*                                                                              47 ± 20*                              Control                                                                        Diabetic 1.3 ± 0.4                                                                             346 ± 123.sup.                                                                        140 ± 152                                                                           29 ± 12                                Control                                                                        Compound A                                                                              0.9 ± 0.5*                                                                            124 ± 29*.sup.                                                                        13 ± 3*                                                                             20 ± 5*                                ______________________________________                                          .sup.a Mean values ± standard deviation                                     *p ≦ .05 as compared to Diabetic Control                           

We claim:
 1. A method of lowering blood glucose in a patient afflicted with diabetes mellitus comprising administering to said patient an effective blood glucose lowering amount of a compound of the formula ##STR3## wherein R₁, R₂, R₃ and R₄ are each independently a C₁ -C₆ alkyl group.
 2. A method of treating a patient afflicted with diabetes mellitus comprising administering to said patient an effective blood glucose lowering amount of a compound of the formula ##STR4## wherein R₁, R₂, R₃ and R₄ are each independently a C₁ -C₆ alkyl group.
 3. A method of claim 1 or 2 wherein the compound is bis(3,5-di-tertiarybutyl-4-hydroxyphenylthio)methane. 